Eddy Current Sensor Coils for Thin Film Detection
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Solution Overview
Problem
Existing eddy current sensors for detecting metal films on semiconductor wafers during polishing face challenges in accurately monitoring thin films without increasing oscillation frequency, amplification degree, or using multiple sensors with different sensitivities, leading to inefficiencies in inspection and processing time.
Innovation Solution
The use of a plurality of coils with different sizes, arranged in specific configurations such as inner and outer coils, connected in series, and wound in single rows and plural layers to enhance sensitivity and accuracy in detecting eddy currents across varying areas on the substrate, allowing for simultaneous and continuous monitoring of film thickness without increasing oscillation frequency or amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single eddy current sensor is used for detecting metal films during polishing, then the device complexity is low, but the measurement precision is insufficient for thin films
Solution Approach 1:
The eddy current sensor is divided into multiple independent coils (first coil and second coil) with different sizes, each capable of detecting eddy currents in different areas. This segmentation allows the sensor to maintain low complexity while improving measurement precision through multi-point detection.
Solution Approach 2:
The first coil and second coil are arranged in a nested configuration where they overlap in at least one area. This nesting allows both coils to detect eddy currents simultaneously in their respective areas, improving measurement precision without significantly increasing device complexity.
2Measurement precision
If multiple sensors with different sensitivities are used to detect varying areas, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
Instead of using multiple separate sensors, the invention segments a single sensor into multiple coils with different sizes. Each coil detects eddy currents in different areas, providing comprehensive coverage without requiring multiple independent sensor units.
Solution Approach 2:
The multiple coils within the single eddy current sensor perform different detection functions (different areas and sensitivities) while being part of the same sensor unit. This multi-functionality allows the system to achieve comprehensive detection precision without increasing the number of separate sensors.
3Measurement precision
If inspection is performed after the wafer is moved away from the polishing pad, then the measurement precision is adequate, but the productivity decreases due to increased processing time
Solution Approach 1:
The eddy current sensor performs preliminary detection of the metal film thickness during the polishing process itself, before the wafer is moved away from the polishing pad. This allows for real-time monitoring and immediate identification of polishing endpoint, eliminating the need for separate post-polishing inspection steps.
Solution Approach 2:
The detection action continues uninterrupted during the polishing process. The eddy current sensor continuously monitors the metal film thickness as polishing occurs, maintaining the useful action of both polishing and detection simultaneously, thereby improving productivity without compromising measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables high-accuracy detection of thin metal films, reduces processing time by allowing for real-time inspection and additional polishing during the polishing process, and improves sensitivity without increasing oscillation frequency or amplification, thereby enhancing the overall efficiency of the CMP process.
Implementation Method 1
an eddy current sensor disposed near a metal film or a conductive film formed on a substrate to detect an eddy current generated in the metal film or the conductive film
Implementation Method 2
the plurality of coils are configured to detect respective eddy currents generated in the metal film or the conductive film
Data Source
AI summary
An eddy current sensor is used for detecting a metal film (or conductive film) formed on a surface of a substrate such as a semiconductor wafer. The eddy current sensor is disposed near the metal film or the conductive film formed on the substrate to detect an eddy current generated in the metal film or the conductive film. The eddy current sensor includes a plurality of coils having different sizes formed by winding a wire or a conductive material. The plurality of coils includes an inner coil and an outer coil spaced from each other, and the outer coil is configured to surround the inner coil. The plurality of coils are configured to detect respective eddy currents generated in the metal film or the conductive film.